1. Field of the Invention
The present invention relates to a portable timepiece in which there is a possibility of the inner pressure of the timepiece exterior assembly being enhanced as in the case of a diver's watch for saturation diving.
1. Background Information
There is known a diver's watch for saturation diving in which, to cope with a case in which the inner pressure of the timepiece exterior case has become higher than the outer pressure thereof, a button of an exhaust valve provided to the case is intentionally depressed, thereby making it possible to forcibly discharge the gas inside the timepiece exterior case to the exterior of the case (See, for example, JP-A-5-172956 Patent Document 1).
The exhaust valve with which this diver's watch is equipped has a stepped hole formed in the case band of the timepiece exterior case, a button, a snap ring, a coil spring, and packing.
The small diameter hole portion of the stepped hole is open to the inner side of the case band, and the large diameter hole portion of the stepped hole is open to the outer side of the case band. The button has an operating portion fit-engaged with the large diameter hole portion, and a shaft portion passed through the small diameter hole portion. The snap ring, which prevents detachment of the button from the stepped hole, is connected to the shaft portion inside the timepiece exterior case. The coil spring is accommodated in the large diameter hole portion while wrapping the shaft portion, and urges the button toward the exterior of the case band. The packing is fixed to the shaft portion. In the normal state in which the button is not pushed in, this packing is in contact with the inner surface of the small diameter portion or of a pipe attached to this hole portion, and exhibits interference; and, in the state in which the button has been pushed in, it is arranged inside the case band and exhibits no interference.
Thus, simultaneously with the pushing-in of the button, the packing is moved so as to be detached from the small diameter portion of the stepped hole into the interior of the timepiece exterior case, and communication is established between the interior and exterior of the case band via the stepped hole. As a result, it is possible to discharge the gas inside the timepiece exterior case to the exterior of the case via the stepped hole.
In a situation in which the button of the exhaust valve is pushed in after saturation diving using the diver's watch of Patent Document 1, there is a possibility of water having been accumulated in the large diameter hole portion of the stepped hole, and, at the same time, the water adhering to the wet hand of the diver may be allowed to enter the large diameter hole portion. Further, in the exhaust valve pushing-in operation under rainy weather, rain water may be allowed to enter the large diameter hole portion. When the exhaust operation is performed in such a situation, there may be a possibility of the water in the large diameter hole portion entering the timepiece exterior case immediately after the completion of exhaust, with the packing exhibiting no interference.
Further, when the button of the exhaust valve is erroneously operated and the exhaust valve is opened, there is a fear of water entering the timepiece exterior case via the stepped hole simultaneously with the completion of exhaust.
As described above, in the prior art technique, there is a fear of water being allowed to enter the interior of the timepiece exterior case from the outside as the degassing operation is performed.